If you said that the mystery duck from yesterday was a mallard, a weird mallard hybrid, a shoveler of some sort, or blah blah blah, then shame shame shame on you: you are a loser. If, however, you said it was a Meller’s duck Anas melleri, then well done, you are some kind of freakin’ duck genius, champion of your peers, wunderkid, and all round sterling human being. Yes, it was Meller’s duck, an endemic Madagascan species that inhabits the lakes, rivers, streams, ponds and wetlands of the eastern side of the central plateau, being associated in particular with Lac Alaotra (Madagascar’s largest lake) [adjacent Joseph Wolf illustration from wikipedia]. It also occurs on Mauritius, where the introduced population is said to be close to extinction (an introduction date of around 1850 was suggested by Meinertzhagen). An introduction attempt on Réunion was unsuccessful. So, well done Mo Hassan (of The Disillusioned Taxonomist), ObSciGuy (of The Obligate Scientist), Alan (of zoo volunteer), and John Harshman.
The big giveaway is the proportionally long, blue-grey bill with its black nail (well done ObSciGuy Paul), though if you could see the green, white-bordered speculum (which you couldn’t…), it would help. Note also that a supercilium is absent, in contrast to the condition in mallards. In male Meller’s ducks, the two central tail feathers are longer than the other tail feathers, and are entirely black, whereas in females these central tail feathers are shorter and brown-edged (Young 1991). Males also tend to have longer heads and bills, and they also have black edges to the bill’s base (Lohan & Young 2004). This captive specimen – photographed at the Isle of Wight Tiger and Lemur Sanctuary – is the first and only one I’ve ever seen, and because I think I can see black edges to the bill base I reckon this is a male. It came to the Isle of Wight collection from Jersey Zoo, where a breeding population of about 230 birds have been reared from 13 individuals caught in the wild between 1994 and 2001 (Young 2005). There were apparently two birds in the enclosure but I could only see one. Anyway, I’m a big duck fan, so seeing a live specimen was a big deal for me. It was particularly frustrating to see an endless stream of zoo visitors take a quick look at it, announce frustration or puzzlement at the presence of a mallard in a zoo devoted to exciting tropical animals, and to walk off without any attempt at self-education (it’s not as if the sign wasn’t obvious: it’s shown below. You had to go to the trouble of rotating your head slightly to the left to see it).
After being named as a new species in 1865*, Meller’s duck had a bit of a rocky ride. Its superficial similarity to the Mallard A. platyrhynchos has meant that various authors have regarded it as a mallard subspecies, or even just as a local variant and not even as a subspecies. These hypotheses went hand-in-hand with the widespread idea that the various non-dimorphic, mallard-like ducks of the world’s oceanic islands were simply the sedentary products of mallard migration: in other words that they were degenerate mallards. Viewed as simply a local mallard variant, Meller’s duck was not deemed to be worthy of conservation effort. Luckily, this idea was not accepted by everyone, and DNA sequencing has demonstrated that Meller’s duck belongs to a distinct lineage that does not fall into A. platyrhynchos (Young & Rhymer 1998). This view of distinct species status is consistent with the fact that it also exhibits behavioural and morphological autapomorphies (Young & Rhymer 1998, Young 1999).
* It’s named for Charles James Meller, the surgeon on David Livingstone’s East African expedition. Meller collected two of the ducks in 1862 but misidentified them as Red-billed pintails A. erythrorhyncha (Young & Rhymer 1998, Young 2005).
Other non-dimorphic members of the mallard group – namely the Yellow-billed duck A. undulata and African black duck A. sparsa – appear basal relative to the Meller’s duck + mallard clade. An interesting consequence of this phylogenetic hypothesis is that the strong sexual dimorphism present in the mallard must (well, ‘must’) have evolved from a non-dimorphic condition, rather than the other way round. It has been hypothesised that absence of a dimorphic plumage (and hence an absence of an eclipse plumage) is advantageous for sedentary tropical and subtropical ducks, as it means that they’re able to breed whenever conditions are suitable; in contrast, sexual dichromatism works well in more predictable, seasonal habitats. Alternative hypotheses have posited that dull plumages have evolved in populations where parental investment from males is higher, that ‘isolating mechanisms’ have been lost as ‘confusable congeners’ no longer occur, or that monochromatism is paedomorphic and linked pleiotropically to paedomorphosis in the wing skeleton (see Livezey 1991). However, the last three hypotheses all assume that dichromatism is the primitive state and monochromatism is derived, rather than vice versa [adjacent pic shows captive Meller’s duck at Cologne Zoo, from wikipedia].
Meller’s duck is one of three waterfowl species endemic to Madasgascar: the others are the recently rediscovered Madagascar pochard Aythya innotata and the Madagascar or Bernier’s teal Anas bernieri (there is also an endemic subspecies of White backed duck, Thalassornis leuconotus insularis). Two additional Madagascan endemics – Greater Madagascan sheldgoose Centrornis majori and Lesser Madagascan sheldgoose Alopochen sirabensis – are extinct. Numerous other taxa occur (or occurred) in the region as well, and it seems that the western Indian Ocean was an important region in waterfowl biogeography. The human colonisation of the region resulted in the decline and extinction of many waterfowl populations. However, Madagascar seems to have become increasingly arid within the last millennium, and this may also have contributed to waterfowl decline (Young & Kear 2006).
For other Tet Zoo articles on ducks and other anseriforms see…
- Duck humps dog, and other stories from the world of waterfowl sex
- Ridiculous super-elongate, coiled windpipes allow some birds to function like trombones – – or is it violins?
- Harbour seal kills and eats duck
- STOP ‘feeding’ the ducks
- Attack of the flying steamer ducks
- Meteoroid vs goose… again
- 2007: a good year for terror birds and mega-ducks
- Tet Zoo picture of the day # 10 (on Swan goose)
Refs – –
Livezey, B. C. 1991. A phylogenetic analysis and classification of recent dabbling ducks (Tribe Anatini) based on comparative morphology. The Auk 108, 471-507.
Lohan, C. & Young, H. G. 2004. Sexual dimorphism and individual variation in the bill markings of Meller’s duck, Anas melleri. Ostrich 75, 176-177.
Young, G. H. 1991. Sexual dimorphism in Meller’s duck Anas melleri. Bulletin of the British Ornithologists’ Club 111, 225-228.
– . 1999. Comparative study of the courtship displays of Meller’s duck Anas melleri, Yellowbilled duck A. undulata and Northern mallard A. platyrhynchos. Ostrich 70, 117-122.
– . 2005. Meller’s duck Anas melleri. In Kear, J. & Hulme, M. (eds) Bird Families of the World: Ducks, Geese and Swans. Vol. II. Oxford University Press, pp. 543-545.
– . & Kear, J. 2006. The rise and fall of wildfowl of the western Indian Ocean and Australasia. Bulletin of the British Ornithologists’ Club 126A, 25-39.
– . & Rhymer, J. M. 1998. Meller’s duck: a threatened species receives recognition at last. Biodiversity and Conservation 7, 1313-1323.